Lung Disease & Respiratory Health Center

Tools & Resources

Sputum Culture

Guide

A sputum culture is
a test to detect and identify bacteria or
fungi (plural of fungus) that are infecting the lungs
or breathing passages. Sputum is a thick fluid produced in the lungs and in the
airways leading to the lungs. A sample of sputum is placed in a container with
substances that promote the growth of bacteria or fungi. If no bacteria or
fungi grow, the culture is negative. If organisms that can cause infection
grow, the culture is positive. The type of bacterium or
fungus will be identified with a microscope or by chemical tests.

If bacteria or fungi that can cause infection grow in the culture, other
tests may be done to determine which antibiotic will be most effective in
treating the infection. This is called susceptibility or
sensitivity testing.

This test is done on
a sample of sputum that is usually collected by coughing. For people who can't
cough deeply enough to produce a sample, they can breathe in a mist solution to
help them cough.

Why It Is Done

A sputum culture is done to:

Find and identify bacteria or fungi that are
causing an infection (such as
pneumonia or
tuberculosis) of the lungs or the airways leading to
the lungs. Symptoms of a lung infection may include difficulty breathing, pain
when breathing, or a cough that produces bloody or greenish brown
sputum.

Identify the best
antibiotic to treat the infection (sensitivity
testing).

Monitor treatment of an infection.

How To Prepare

Do not use mouthwash before collecting a
sputum sample because it may contain antibacterial substances that could affect
your results.

If
bronchoscopy will be used to collect your sputum
sample, your doctor will tell you how soon before the test to stop eating and
drinking. Follow the instructions exactly about when to stop eating and drinking, or your surgery may be canceled. If your doctor has instructed you to take your medicines on the day of surgery, please do so using only a sip of water.